It is well known that sand can be used as a mold for metal castings. An organic binder is mixed with the sand to allow the sand to be formed into a mold. Molten metal is then poured into the mold. When the metal cools, the sand mold is removed, leaving the finished metal part.
The sand can be removed from the metal casting mechanically or thermally. Mechanical removal entails shaking the mold until it breaks apart, or physically tearing the mold off the metal part. Thus, mechanical removal can damage the metal part. In addition, the metal part is generally heat treated after it cools, which can be done in combination with thermal removal of the sand mold. For these reasons, thermal means are generally the preferred method used to remove the sand mold.
Thermal removal comprises placing the mold and the casting in a thermal sand removal oven. The mold and casting are heated with a stream of hot air, generally at high velocity. The hot air causes the organic binder to combust, releasing the sand. The sand then falls off the castings due to gravity, although some portion of it is mixed into the air stream. The air stream is generally at a high velocity to increase the speed of the removal of sand from the castings. To increase the speed of the air stream, fans are generally used to blow the hot air over the castings. The air is generally recirculated to keep the air temperature high, reducing the cost of heating the oven. This leads to the problem of the sand being recirculated with the air. The recirculated sand damages the fan blades, or whatever means are used to recirculate the air. This damage increases the cost of running the oven, and increases the downtime of the oven due to the maintenance needed.
Clearly, then, there is a longfelt need for an apparatus to separate the sand from the air stream in a thermal sand removal oven.